As Barron Park residents know all too well, residential streets and industrial operations often make for a toxic mix when it comes to neighborhood harmony.

A decade ago, residents of Chimalus Drive became alerted to that fact when they detected a noxious odor in the air. The smell turned out to be nitric-acid gas that was released by Communications & Power Industries (CPI), a manufacturer of microwave- and radio-frequency products that operates a plating shop on Hansen Way. Residents became further alarmed in March of 2008, when the company spilled about 20 gallons of hydrochloric acid into its rear driveway, and again two months later, when 50 gallons of wastewater containing copper and nickel were inadvertently released into Matadero Creek.

Though there haven't been any reported incidents at CPI since 2008 and the company has significantly reduced the quantity of deadly chemicals it uses, concerns about the toxins being stored so close to homes remain widespread in Barron Park. On Monday night, the City Council will consider the most dramatic action to date to address this concern: a law that would require businesses using high quantities of hazardous materials to be located at least a football field away from residences, schools, day care centers and other areas where occupants may be particularly susceptible to the effects. In addition, council members will consider a separate ordinance that would require CPI to relocate or close its plating shop by 2026.

The council's Nov. 16 discussion will follow years of studies and counter-studies, pleas from residents and protests from CPI. In 2012, CPI argued in a letter that its recent facility upgrades and its March 2012 decision to reduce the quantities of stored hazardous materials have greatly enhanced safety. According to CPI, processing tanks were equipped with seismic anchors, certain storage tanks were relocated and an assortment of sensors, scrubbers and monitoring systems were installed to create what the CPI report calls "an advanced, state-of-the-art facility with layers of redundant safety technologies."

Given these proactive steps, CPI argued in a letter, "There is no rational or reasonable basis for the city to consider the termination of CPI's vested use of its property by way of a zoning amendment and then amortizing its use."

"CPI has a tremendous investment in its facility and an ongoing interest in operating safety for the benefit of its employees, nearby residents, other users of Stanford Research Park and the community at large," the letter states. "CPI will not abandon a facility that has served as the headquarters for its business for almost 60 years and where it conducts the majority of its most important manufacturing."

Over the past five years, both the city and CPI commissioned further studies followed by supplemental studies in hopes of determining just how dangerous the facilities are. The city's consultant, AECOM, evaluated five different hypothetical disaster scenarios, including two "extreme" situations. The only one that was shown to pose a potential problem was the release of nitric acid, which could affect people's health up to 92 feet from the release point. Then last year, in response to Barron Park residents' concerns, AECOM did additional analysis that considered a massive earthquake that could result in a damaged building and a mixing of chemicals at the CPI site. The scenario, which AECOM deemed "highly unrealistic," was shown to potentially affect residences up to 616 feet away.

CPI's consulting firm then came back with its own analysis showing that an earthquake of this magnitude has a 0.75 percent chance of occurring over the next 50 years. In its August 2014 report, the firm Albus-Keefe and Associates noted that this probability is well below the state code, which requires similar structures to be designed for earthquake events "with a probability of exceedance equal to 2 percent in 50 years."

These assurance, have done little to assuage concerns from the community and the council, which decided in October 2014 to move ahead with the amortization. In addition, the council directed staff to put together a broader ordinance that would regulate hazardous materials in close proximity to residential zones.

The decision came despite assurances from CPI President Bob Fickett that "we are not the enemy" and that CPI "take(s) the health of the community and our employees very seriously."

"In the 60 years, there's never been any harm to any community members," Fickett said.

On the other side of the debate were the roughly 20 residents from Barron Park who came to support the amortization. Lydia Kou framed it as an issue of health and told the council that "it's time to put the residents first," while Samir Tuma called the existing proximity between the plating shop and the neighborhood an "unsafe situation." Ultimately, the council voted 8-0 to move ahead with amortization.

"In the end, it comes down to the safety of the people who live in our community, and we're in charge of that safety," Councilwoman Liz Kniss said during the October 2014 hearing.

Now, the council will have a chance to review and possibly approve the two proposed ordinances, which were the subject of a community meeting last month. If it votes to support both, it would spell the beginning of the end for CPI's plating shop as well as the beginning of a new process for reviewing manufacturers looking to set up shop near schools and homes.

The most significant change in the broader hazardous-materials ordinance is a new tier, called "Tier 2," for companies that use toxic materials in quantities that exceed the city's threshold and that use substances deemed as "toxic" or "extremely hazardous" by state and federal regulators. This tier would include 14 facilities in Palo Alto, four of which are buildings on the CPI campus. The change would reform the current system, which includes two tiers but in which every one of the more than 400 companies with hazardous materials is classified in the lower tier.

In addition to the CPI buildings, the list of facilities that would fall under the new Tier 2 includes buildings operated by Genencor International, Hammon Plating, Hewlett Packard, ONED Materials, the Palo Alto Research Center, Space Systems Loral and Target Discovery.

Aside from CPI, none of the companies that would be classified as Tier 2 are located close enough to residential areas for concern, based on the proposed ordinance. But the new law would ensure that new Tier 2 facilities would not be allowed within 300 feet of "residences, schools, daycare facilities, homes for the elderly, convalescent homes and similar uses whose occupants may be more susceptible than the general population to adverse effects of exposure to toxic chemicals and other pollutants."

Similarly, schools, residences and other such organizations would be prohibited from locating in industrial zoning districts within 300 feet of Tier 2 facilities.

The new ordinance would also have a third tier, which would cover users whose hazardous materials exceed even higher thresholds the ones outlined in the California Accidental Release Program. Currently, no facilities of this sort exist in Palo Alto, according to a report from the Department of Planning and Community Environment.

An inventory put together by the Palo Alto Fire Department and its consultant, AECOM, shows that while CPI isn't the only facility with high levels of hazardous materials, it has by far the the greatest variety of toxic chemicals. Between them, CPI's four Tier 2 buildings house 36 chemicals that are deemed "toxic" or "highly toxic." One of these buildings, the plating shop, uses 18 such chemicals. The shop is also the only one of the four that is listed as having "extremely hazardous substances." Another CPI facility, known as Building 1B, is listed as using 15 chemicals deemed "toxic" or "very toxic." No other building on the 14-facility list uses more than four such chemicals.

If the council approves the new ordinance, the three CPI buildings that stand within 300 feet of the Barron Park homes would be deemed "legal and non-conforming," which means they once complied with the city's zoning laws but no longer do so. However, CPI would not need to relocate them.

The new ordinance would also categorize 419 companies under Tier 1, a list that includes gas stations, nail salons, paint retailers and manufacturing businesses. Unlike Tier 2 companies, these businesses use hazardous materials that are not deemed "toxic or highly toxic by the state Fire Code" or classified as using "extremely hazardous substances" by federal regulators. Tier 1 companies would continue to be governed under the city's existing program, which requires each of the facilities that store, use or handle more than 55 gallons, 500 pounds or 200 cubic feet of regulated material to submit to the city a "Hazardous Materials Business Plan" that lists the inventory of chemicals used.

The ordinance calling for CPI to phase out its plating shop by 2026 could mean the shop's closure or relocation to a different part of the campus that its at least 300 feet away from residents. The deadline is based on an amortization study that the city commissioned in 2012, which concluded that 20 years would be a reasonable termination date, with the countdown starting in 2006, when CPI last made a major upgrade to the plating shop.

CPI, for its part, argued that amortization should be based on at least a 40-year period. In its own study, the company argued in 2012 that it can "neither move its plating process from its current campus location, outsource its plating process to another location/vendor, nor move its entire manufacturing plant elsewhere without significant detrimental financial loss in investment to CPI."